Gallium nitride (GaN) thin film crystal draws attention as excellent blue light-emitting devices, has been used as a material for light-emitting diodes and expected as a blue-violet semiconductor laser device for an optical pickup. Recently, it draws attention as a semiconductor layer constituting electronic devices, such as high-speed IC chips, used for mobile phones or the like.
According to Patent document 1 (Japanese Patent No. 4223540B), upon growing a crystal of a nitride of a group 13 element by Na flux method, it is described to use germanium metal as a dopant. Further, according to Patent document 2 (Japanese Patent publication No. 2010-001209A), it is proposed to use germanium metal, as well as carbon, as dopants into a crystal of a nitride of a group 13 element in Na flux method, so as to grow an n-type single crystal having a high electron density.